There is conventionally known a loudness controller as a device for correcting auditory sensitivity with respect to sound volume (refer to, e.g., Patent Document 1). The loudness controller divides the frequency band of an audio signal into three ranges: low, middle, and high frequency ranges, then changes the gains of the low, middle, and high frequency ranges in conjunction with the main volume, and synthesizes the audio signals of the respective frequency ranges to achieve correction of the auditory sensitivity. The loudness characteristics are thus realized by changing the volumes of the respective frequency bands track in conjunction with the entire volume change. That is, by making sound quality, balance control, fader control, etc., in conjunction with the entire volume change, optimum acoustic environment can be achieved. In particular, auditory sensitivity correction taking into account also a special reproduction condition required for an on-vehicle application or the like can be achieved.